Abstract
Stratigraphic drilling from the McMurdo Ice Shelf in the 2006/2007 austral summer recovered a 1284.87m sedimentary succession from beneath the sea floor. Key age data for the core include magnetic polarity stratigraphy for the entire succession, diatom biostratigraphy for the upper 600m and 40Ar/39Ar ages for in-situ volcanic deposits as well as reworked volcanic clasts. A vertical seismic profile for the drill hole allows correlation between the drill hole and a regional seismic network and inference of age constraint by correlation with well-dated regional volcanic events through direct recognition of interlayered volcanic deposits as well as by inference from flexural loading of pre-existing strata. The combined age model implies relatively rapid (1m/2-5ky) accumulation of sediment punctuated by hiatuses, which account for approximately 50% of the record. Three of the longer hiatuses coincide with basin-wide seismic reflectors and, along with two thick volcanic intervals, they subdivide the succession into seven chronostratigraphic intervals with characteristic facies:1.The base of the cored succession (1275-1220mbsf) comprises middle Miocene volcaniclastic sandstone dated at approx 13.5Ma by several reworked volcanic clasts;2.A late-Miocene sub-polar orbitally controlled glacial-interglacial succession (1220-760mbsf) bounded by two unconformities correlated with basin-wide reflectors associated with early development of the terror rift;3.A late Miocene volcanigenic succession (760-596mbsf) terminating with a ~1my hiatus at 596.35mbsf which spans the Miocene-Pliocene boundary and is not recognised in regional seismic data;4.An early Pliocene obliquity-controlled alternating diamictite and diatomite glacial-interglacial succession (590-440mbsf), separated from;5.A late Pliocene obliquity-controlled alternating diamictite and diatomite glacial-interglacial succession (440-150mbsf) by a 750ky unconformity interpreted to represent a major sequence boundary at other locations;6.An early Pleistocene interbedded volcanic, diamictite and diatomite succession (150-80mbsf), and;7.A late Pleistocene glacigene succession (80-0mbsf) comprising diamictite dominated sedimentary cycles deposited in a polar environment.
Original language | English (US) |
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Pages (from-to) | 189-203 |
Number of pages | 15 |
Journal | Global and Planetary Change |
Volume | 96-97 |
DOIs | |
State | Published - Oct 2012 |
All Science Journal Classification (ASJC) codes
- Global and Planetary Change
- Oceanography